1. Field of the Invention
The present invention relates in general to an indirect cathode sleeve and manufacturing method thereof, and more particularly to an indirect cathode sleeve and manufacturing method thereof capable of substantially reducing electric power consumption of a heater which is disposed inside the cathode sleeve and simultaneously reducing a picture-producing time by making an inside surface of the cathode sleeve oxidized and an outside surface thereof reduced.
2. Description of the Conventional Art
Conventionally, with reference to FIG. 1, a hollow cathode sleeve 2 which has the top closed, is shown. A cathode sleeve support 5 having a hollow and larger diameter than that of the cathode sleeve 2 surrounds the cathode sleeve 2, specially a predetermined upper and lower portions thereof are affixed to the outside surface of the cathode sleeve 2. A plurality of heaters 3 are disposed inside the cathode sleeve 2 and electrically connected with a power supply. A cap-shaped controlling electrode G1 is fixedly disposed above but not touching the top of the cathode sleeve 2 for controlling the on-off state of an electron beam which is generated at the cathode sleeve 2, additionally having a hole 7 disposed at the center portion thereof with a predetermined diameter for passing the electron beam. An upside down cap-shaped accelerating electrode G2 is fixedly disposed above but not touching the controlling electrode G1 for accelerating the electron beam, additionally having a hole 6 disposed at the center portion thereof with a predetermined diameter for passing the electron beam. Here, the outer edge of the accelerating electrode G2 is affixed to the body(not shown) of the cathode sleeve 2. A condensing electrode G3 is disposed above but not touching the accelerating electrode G2 for condensing the electron beam generated at the cathode sleeve 2 and affixed to the accelerating electrode G2, additionally having a hole 8 disposed at the center portion thereof with a predetermined diameter for condensing and passing the electron beam which is passed through the controlling electrode G1, the accelerating electrode G2 and the condensing electrode G3, in order.
The operation of the conventional cathode sleeve 2 will now be explained.
When electric power is applied to the heater 3, it becomes heated, and an electron beam is generated due to a chemical reaction between a base metal 1 and the electron-emitting material(not shown). The quantity of the electron beam generated is first controlled by the controlling electrode G1. The controlled electron beam enters into the accelerating electrode G2 through the hole 7. The electron beam that enters into the accelerating electrode G2 is accelerated thereby and passes the hole 8 and enters into the condensing electrode G3. Where the electron beam is condensed. With reference to FIG. 2A to FIG. 2C, the conventional bimetal type of indirect cathode sleeve and manufacturing methods thereof are shown.
Referring to FIG. 2A, the forming step of the conventional bimetal type of indirect cathode sleeve is shown. The Nickel alloy which is made of Nickel(key component), Magnesium, Silicon, and Tungsten used as a reducing components, is formed at the outside surface of the cathode sleeve. The Nickel-Chrome alloy 13 is formed at the inside surface of the cathode sleeve.
Referring to FIG. 2B, the etching step of the conventional bimetal type of indirect cathode sleeve is shown. Through the etching step, a predetermined outside surface of the cathode sleeve is unetched by masking it and the remaining surface is etched, that is, the surface unetched remains a bimetal type structure and then the surface etched remains a Nickel-Chrome alloy. In the drawings, reference numeral 22o denotes the outside surface of the cathode sleeve and 22i denotes the inside surface of the cathode sleeve.
To begin with, the etching step will now be explained.
The etching step is well known from U.S. Pat. Nos. 4,376,009 and 4,441,957. According to these patents, a predetermined surface of the top of the cathode sleeve 22 is completely masked with an acid-resistant material such as silicon rubber. A bar is inserted into the cathode sleeve 22 through the bottom thereof in order to sealingly prevent the inside surface of the cathode sleeve 22 from the etchant during etching. Thereafter, the etchant floods the cathode sleeve 22, so that the unmasked surface thereof is etched and the masked surface thereof is unetched. As a result, shown in FIG. 2B, the top of the cathode sleeve 22 appear as having a cap-shaped head.
With reference to FIG. 2C, a base metal 12a made of Nickel alloy is formed at the top of the cathode sleeve 22. An electron-emitting material layer 4 is formed at the outside surface of the base metal 12a. Here, the electron beam is generated from a chemical reaction between a metal 12a and the electron-emitting material 4.
However, studies on how to reduce the picture-producing time and decrease electric power consumption of the heater(not shown) have been conducted. Here, the picture-producing time denotes the time it takes from supplying power to the heater to producing an image onto the screen. As a result, another embodiment of the conventional indirect cathode sleeve and manufacturing method thereof is developed. As shown in FIGS. 3A to 3C, it is related to make an outside/inside surface of the cathode sleeve 22 oxidized, that is, to form the inside thereof black having a high heat radiating rate, whereby the picture-producing time and the heater consumption electric power are both reduced. Referring to FIG. 3A, the forming step is to form the inside surface of the cathode sleeve 23 with a Nickel-Chrome alloy and the outside surface of the cathode sleeve with a Nickel alloy. Here, the cathode sleeve 23 is a bimetal and has the top opened. A cap-shaped base metal 13a is formed at the top of the cathode sleeve 23. Referring to FIG. 3B, the heat process is to make the inside/outside surface of the cathode sleeve 23 oxidized by oxidizing the Chrome component which is included therein. Referring to FIG. 3C, an electron-emitting material layer 13a is formed at the outside surface of the base metal 13a.
Typically, the cathode sleeve made of the Nickel alloy should have a dew point of the heat process hydrogen of over -40.degree. C., where the Chrome is oxidized. At this time, the state of the cathode sleeve is called an oxidizing state. The level of the oxidization of the cathode sleeve is greatly based on the dew point of the heat process hydrogen. That is, strong oxidization is achieved as the dew point of the heat process hydrogen is high, so that the heat radiating rate become high and thus the picture-producing time becomes quicker. However, if overoxidiazation is conducted, the base metal is simultaneously oxidized, so that the desired effects of the oxidization is reduced due to heat damages. In this case, as shown in FIG. 1, the welding step cannot be conducted at the portion where the cathode sleeve 2 is welded to the cathode sleeve support 5 due to the oxidization of the Chrome at the outside surface of the cathode sleeve 2.
On the contrary, in case that the dew point of the heat process hydrogen is low in a high temperature hydrogen environment, resistance welding is possible between the cathode sleeve 2 and the cathode sleeve support 5, so that the electric power consumption of the heater 3 will be reduced. However, if the oxidization condition of the cathode sleeve 2 is weak and the heat radiating rate is low, consequently the improvement of the picture-producing time cannot basically be achieved.
In addition, in order to make the cathode sleeve 22 be equipped with the oxidization state having the best heat radiating rate, the dew point of the heat process hydrogen in the high temperature wet process environment should be over 0.degree. C., in addition, the dew point of the heat process hydrogen in the high temperature wet process environment in order to prevent the electron-producing characteristics from heat damage by the oxidization of the base metal should be below 20.degree. C. In case that the dew point of the heat process hydrogen is between 0.degree. C. and 20.degree. C., the heat radiating rate should maintain 80%. In addition, in case that the dew point of the heat process hydrogen is below -40.degree. C., the heat radiating rate increases four times, and in addition the picture-producing time is reduced by 2 seconds.
However, if the cathode sleeve 22 is oxidized in a state that the heat radiating rate is high, as previously noted, the resistance welding properties become poor.
With reference to FIG. 2, since the dew point of the heat process hydrogen of the conventional bimetal type of the indirect cathode sleeve is between -35.degree. C. and -25.degree. C., both the outside and inside surface of the cathode sleeve 22 are oxidized, but in case the level of the oxidization condition is low, even though the resistance welding is possible between the cathode sleeve 22 and the cathode sleeve support 5, increasing the picture-producing time is difficult because the heat radiating rate is below 40%.
To resolve the problems of the conventional bimetal type of the indirect cathode sleeve as shown in FIG. 2, another embodiment of the cathode sleeve as shown in FIG. 3 is well known. The conventional cathode sleeve with the top opened is made of a Nickel-Chrome alloy inside and a Nickel alloy outside. Thereafter, the top thereof is formed with a cap-shaped base metal 13a. The inside surface thereof is oxidized and the outside is reduced, leaving the inside black and the outside white. In this case, even though the desired effects of getting a high heat radiating rate inside and a low heat radiating rate outside as well as a rapid picture-producing time are achieved, the cathode sleeve is thicker, thus the manufacturing costs is high and the manufacturing time will be prolonged due to its complicated structure. In the conventional cathode sleeve, when making the cathode sleeve thinner, during a high temperature process, the structure of the cathode sleeve will be changed in its size and appearance.